There are around 600 million people over the age of 60 across the globe; a figure which is expected to double by 2025, according to the United Nations.

The organisation has designated October 1 as International Day of Older Persons (IDOP). UK Older People's Day is also held on October 1 each year, to celebrate the contributions of older people to society.

To mark IDOP 2015, here are nine facts you may not know about older people.

1. There were more than half a million people aged 90 and over living in the UK in 2014, almost triple the number thirty years ago.

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2. For every 100 people aged 90 and over in 2014, 29 were male and 71 were female.

3. The number of centenarians (people aged 100 and over) living in the UK has risen by 72% over the last decade to 14,450 in 2014.

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4. Male life expectancy has increased from 70.8 in 1980-82 to 79.1 in 2012-14. Female life expectancy has increased from 76.8 to 82.8 during the same period.

5. The most common age of death was 86 years for men and 89 years for women. This is higher than current average life expectancy at birth.

6. Men aged 85 in 2012-14 could expect to live to 90.8 whereas women could expect to live to 91.8.

7. Three in 10 of those aged 80 and over reported being lonely in 2014 to 2015.

8. A third of those over 80 reported very high levels of life satisfaction in 2014 to 2015.

9. Around 1 in 10 (11%) of those aged 75 and over reported having no close friends in 2011 to 2012.